The present invention is directed to infusion packages, especially tea packages and the like, and more particularly to an infusion package constructed of a non-woven, fiber-free, perforated thermoplastic film or other porous material.
The invention is particularly concerned with an infusion package constructed of a coextruded multilayer perforated thermoplastic film having a plurality of uniform minute holes or openings therein, which has a relatively flat configuration for packing and which can be readily converted to a dual chamber or flow-through type bag.
At the present time, most tea bags or packages commercially marketed are either the "pillow" pack type or the dual bag or Flo-thru.RTM. type. The bags are made of paper and the latter have strings and tabs attached thereto by staples or glue. Although a considerable degree of success has been achieved with these two types of bags, they have poor wet strength. The single compartment or "pillow" tea bag is a flat bag of liquid pervious material which contains sufficient tea for an individual serving or for multiple servings in the case of the larger packages used by food service industries. The tea spreads the sides of the bag to accommodate the contents. When the tea is wet, it forms a swollen compacted mass that may fill the bag. The swelling tea presses outwardly against the inside walls of the bag. Squeezing or other external pressure on the bag may cause it to break open or split or otherwise undesirably dispel its contents. To overcome this swelling, some bags have been constructed with pleats therein. Although effective to some degree, they have a lack of wet strength and present other problems.
The art is replete with infusion packages containing two or more fill containing segments. The connected segments permit liquid flow between the segments and expose a greater bag surface area to liquid for extraction therethrough. Although such bags may improve brewing, they have the same lack of wet strength of the "pillow" type bags, and present other problems, such as assembly and packaging.
Infusion-type tea packages are usually rectangular packets or sachets made from single or multiple pieces of paper crimped or otherwise sealed along the edges. In another type, a single strip of paper is folded twice longitudinally to form an inner centrally disposed double fold joining the two meeting edges. In a type of flow-through tea bag, a triple transverse fold intermediate the length of the folded strip forms two pockets which are partially filled with tea before the open ends thereof are folded over and stapled to a strand of string usually having a tag on the end thereof.
Over the years, a wide variety of infusion packages or bags, usually for containing tea for subsequent brewing, have been developed. The packages are usually constructed of filter paper or some other type of porous material.
An infusion package which has a natural, expanded or unflattened condition and which is folded to a flattened configuration for packing is disclosed in U.S. Pat. No. 4,290,521. A pull strip with a tab on one end is adhesively attached to the upper part of the package for causing the package to be expanded from its flattened configuration when the strip is pulled.
A type of dosage pack or infusion package having two permeable bags joined to each other along a common seam and arranged in a face-to-face relationship by folding the bags onto one another along a fold line extending in the common seam is described in U.S. Pat. No. 4,055,668. A holder string is positioned between the two bags with one end attached to one of the bags and the other end attached to a tag positioned externally of the two bags.
U.S. Pat. No. 3,899,599 discloses a single chamber or dual chamber tea package which has a flexible strip attached to an exterior side which can be partially removed to provide a hanger for holding the package in place in a container.
An infusion packet having two oppositely disposed, rigidly separated pockets of tea joined together by two tapering end portions which form a narrow, triangular shaped porous cup is shown in U.S. Pat. No. 3,597,222.
U.S. Pat. No. 3,653,913 discloses an infusion bag made from a rectangular strip of porous fibrous material, the longitudinal margins of which are folded together so as to form a longitudinal joint consisting of three layers which are knurled together. The tube is divided by a transverse bend so as to form a pair of chambers for holding an infusible substance, and the opposite ends of the tube are connected to each other so as to close the package.
An early type of tea bag or tea ball wherein the bag is a triangularly-shaped pocket formed from a rectangular strip of perforated aluminum foil is described in U.S. Pat. No. 1,581,578.
Other types of filter paper tea bags or the like with a variety of handles are illustrated in U.S. Pat. No. 2,328,017; U.S. Pat. No. 2,359,292, U.S. Pat. No. 3,566,573; U.S. Pat. No. 4,153,153 and Great Britain Pat. No. 2,087,350. Great Britain Pat. No. 2,053,668 discloses a tea bag having an accordion fold.
Infusion bags with positioning means and flotation means are disclosed in U.S. Pat. No. 3,797,642 and U.S. Pat. No. 3,809,215, respectively. The tea bags themselves may be made of various materials including paper, plastics such as nylon, perforated plastic film, e.g., polyester, or woven or non-woven fabric of natural or synthetic origin.
A percolatable porous bag constructed of a blend of individualized textile or cellulosic fiber and a small amount of thermoplastic fiber is disclosed in Canadian Pat. No. 802,720.
Various degrees of success have been achieved with the foregoing infusion bags or packages, with paper or fibrous bags presently dominating the market place. One of the problems with paper bags is lack of wet strength. Paper packages do not have the strength to withstand squeezing or other pressures commonly applied by consumer or other users.
An infusion bag for items such as tea, coffee or similar food products for brewing must have a number of qualities. It must have an inability to impart a taste factor to the liquid product after brewing. In effect, it must be substantially odorless and tasteless. It must also be sufficiently strong to contain the brewing product in boiling water, e.g., in the steeping of tea, coffee, and similar liquid beverages. The bag must also be porous enough to permit liquid diffusion therethrough, but the pores or openings must be of such size that migration of the beverage material therethrough is inhibited, both when the bag is dry and when the bag has been immersed in a liquid. It is also important that infusion begins to take place within a few seconds and be completed within a few minutes. It is further desirable that a package, bag or sachet, such as a tea sachet, retain sufficient stability that it can be compressed after brewing is completed without destruction of the container.
Thermoplastic films such as polyethylene and polypropylene are common packaging materials. Multilayer films of various types are also quite common packaging materials. The films are generally non-porous and impervious to water and other inert liquids. At least one of the layers of film has strong adhesive qualities. Examples of such multilayer films may be seen in U.S. Pat. No. 4,254,169; U.S. Pat. No. 4,239,826; U.S. Pat. No. 4,233,367; U.S. Pat. No. 3,908,070; U.S. Pat. No. 3,423,231; U.S. Pat. No. 2,817,124 and U.S. Pat. No. 2,817,123.
Perforated thermoplastic films have many useful applications, including packaging of food products such as cheese, gardening and farming to prevent growth of weeds while permitting moisture to be transmitted through the film to the soil beneath and for making absorptive structures such as disposable diapers, for example, see U.S. Pat. No. 3,814,101.
Perforation of thermoplastic films is generally achieved by vacuum perforation of thin plastic films which involves the extrusion of molten polymeric materials such as polyethylene through a slot die. The hot melt web of film exiting the die impinges on a form through which a vacuum is drawn causing the film web to be perforated and holes formed therein. Depending upon the form used, films can be produced which have as few as 50 holes per square inch or which have thousands of holes per square inch. One of the earlier methods for vacuum perforation of plastic film is disclosed in U.S. Pat. No. 3,054,148.
The present invention provides an infusion package or sachet which meets the requirements for tea brewing and additionally overcomes the problems of lack of wet strength and packaging associated with the prior art.